Alternating current arc-welding transformer



Oct. 18, 1938. E. FRlEs I 2,133,919

ALTERNATING' CURRENT ARC-WELDING TRANSFORMER Filed March 4, 1956 25 J 20 13 l I nwmnnn i nun 1 mhh \1\\u\ 8 n. 1 2 5 n il y 1 EL# 6 Patented Oct.l 18, 1938 Y l ALTERNATING CURRENT AEC-WELDING TRANSFORMEB.

Eduard Fries, Oerlikon, Switxerland Application March 4, 193s, serial No. 61,159

In Germany March9, 1935 y.

This invention relates to A. C. arc welding connection and must be such as to provide a path transformers in which the no-load voltage for the reluctance of which is variable in a continustarting and maintaining the arc must be varied ous stepless manner within a predetermined in accordance with thel intensity of the welding range, in order to produce a regulation of the nocurrent. y load voltage in accordance with the known ref In addition welding transformers should permit quirements of A. C. arcs. These latter requireadjustment of the Welding current from for inments are attained either by suitably shaping stance, 15 up to about 220 aniperes, that is to the pole faces which define a variable air gap say, inthe ratio of 1:10 to 1:15. preferably so as to differ from a geometrical lo The welding transformers at present known are plane. and/0r by bridging the air 8&9 by mean-iiv 10 provided `with taps for the adjustment of the of a magnetizable core of reduced section. welding voltages and currents within the above b. By placing around the variable magnetic rementioned limits. For different welding operasistance an auxiliary coil,'which is connected in tions the connections must be shifted to the taps series with the secondary Winding 0f the transwhich give the required voltage or current. For formerso that a variable amount of additional 15 reason of simplicity only two no-load taps are voltage iS induced in the auxiliary C011 et 11G- provided. The capacityv of the transformer is load; the product of the no-load tension and the weld` 'I'he annexed drawing shows several embodiing current. ments of the invention. zo

Other transformers are known which are pro- Figure 1 iS a darammatil View partially in vided with a number of secondary coils adapted section of an A. C. arc welding transformer proto be connected together either in series or in vided with a main and an auxiliary magnetic cirparallel in order to thereby change the characcuit includinga variable air gap encircled by an terlstic. Also, these transformers, however, presauxiliary coil;

ent many inconveniences and do not permit of a Figure 2 is a partial disremmatical view 0f a 25 stepiess or continuous regulation of the no-load part of a transformer core Provided with a varivoltage. able V'air gap, which is bridged by a magnetizable In order to overcome these inconveniences and shunt of reduced section; f.

' to obtain a continuous regulation of the current Figure 3 is another modification of a trans- 3-0 for starting and `maintaining the welding arc former core provided with two variable air gaps 30 without the use of taps on the secondary windand showing in addition a modified arrangement ing, I have devised a transformer design which of the transformer coils; meets the following requirements: Figure 4 is a prospective view of a transformer a.. Possibility of obtaining automatically and core showing another embodiment of a core for continuously and without taps., the most approshunting the air gap and Figure 4a is an elevapriate no-load voltages ranging from v. for the tion of the case transformer showing the posicurrents of greatest intensity to about v. for y tion of the coils on the core; the smallest currents.- i Figure 5 is a diagrammatical view of a transb. By working with substantially lower voltages former for three-phase current;

4 in the secondary winding ofthe transformer, the Figure 6 is a diagram of the electric connecl 4 absorbed apparent power is correspondingly lessH tion and windings of the transformer shown in and a smaller transformer may be employed. Fig. 5, and

c. Practically complete elimination of the vivIi'iizules 'I to 9 show a preferred embodiment of '45 bration of the iron sheets forming the core and antivibrating connection of the movable core of consequently elimination of the hum. the transformer core. A These requirements, which are indispensable f In Figure 1, the numeral I designates the main for a good industrial transformer, are not found limb of the arc welding transformer integral to my knowledge and belief in any of the former with the yokes I' and I", I is the primary windtransformers. ing and i the secondary winding both arranged 5 In practice I have found that a reliable` weldon limb I. Between the yokes I' and I" is 5 'ing transformer should meet the following rearranged' an intermediate limb 2 on which no quirements: t coils are arranged. To the end of one of the a. The transformer core must be pro ded with yokes, I", a movable limb l is hinged at i. An

an auxiliary movable limb or core ch must be auxiliary coil is arranged about the air gap I.

55 connected to the fixed part by 'an antivibration When the transformer is energized with the 55 ing current, but only,to a limited extent, providsecondary circuit open a, magnetic flux is generated between limb I and yokes I and I", the magnetic circuits 'being completed through limbs 2 and 3 as' indicated by the arrows, the magnetic uxes being inversely proportional to the magnetic resistance of the two circuits. The secondary winding 5 is connected in series with thev auxiliary coil "I, so that the magnetic flux passing from limb I through limb 3 induces an additional voltage in the -auxiliary coil 'I at noload which is addedto the voltage of the secondary Winding 5, thereby facilitating the starting of the arc and improving its stability. By reducing the air gap 8, that part of the= magnetic flux generated within limb I which passes through limb 3 is increased and consequently also the supplemental voltage induced within auxiliary coil 'F is'increased. In order to avoid asubstantial leakage of the auxiliary flux and to provide the desired no-load voltage adjustment the pole faces forming the air gap are preferably step shaped.

It is to be noted that the regulation is greatly inuenced by the shape of the pole faces which define the gap, which means that the value of the supplementary voltage induced Within coil l,v

depends also upon the shape of the said pole faces.

During the welding the direction of the iiux in limb 3 is reversed and the auxiliary ux is returned through limb 2, which therefore must be so dimensioned as to allow the passage during the welding of the sum of the magnetic uxes of the limb I and of the limb 3. As the magnetic flux traversing the limb I3 at no-load is desired and useful, the air gap in case of low welding currents may be reduced to zero. From the foregoing it is apparent that the transformer according to the invention permits of varying the welding current within the widest limits without the use of taps.

Figure 2 shows another embodiment of the part of the transformer core including the movable limb 3. According to this embodiment the air gap 8 is bridged by a small laminated core 9, which is so dimensioned as to shunt the air gap y and permit the flow-of a magnetic flux of substantially constant value to pass through the limb 3 thereby generating in the coil 1 a. supplementary voltage which may be as much as 20% of the secondary voltage. This permits of a reduction of about 2(l%l the size of the transformer including the auxiliary coil and the absorbed apparent output isf correspondingly smaller. 'I'he bridge 9 naturally also -aifects the regulationof the1welded, however, that the bridge 3 is so dimensioned lasto become already highly saturated whenthe magnetic flux passing therethrough reaches a value of say about 20% of the normal ux traversing the limb 3. The bridge 9 is, therefore, preferably made of a material presenting a high magnetic permeability and very definite limit of tained by other structural means. """It should also be mentioned that it is possible to vary the ilux traversing the air gap 8 by varying the magnetic resistanoe'of the limb 2. i.

This is conveniently effected by providing an additional air gap in the member 2 of the transformer, as shown by way of example in Figure 3. Thetransformer that-is similar to that shown in Figure 1, has its yoke I' hinged tothe limb I and 'the shiftable-limb 3 hinged as in the other cases secondary windings 4 and 5 may be arranged onv the yoke I or they may be arranged on the yoke I, while the auxiliary coil vjI is preferably arranged around air gap 8.

Figures 4 also 4a show a modified form of the adjustable zone of variable reluctance of the transformer core, which is effected by extending some of the laminations of the transformer in proximity of the air gap 8 vsubstantially'at right angle of the latter so as to form therebetween grooves 20 and 20'., respectively. Adjacent to the rear end of the projections of yoke I' is mounted an angle iron 22. Laminated cores 2I are inserted in the grooves 2U and welded to the angle x30 iron 22. The outer parts of ithese cores project across air gap 8 into grooves 20in which they are fitted with a sliding t. .f

other parts is like 'I'he arrangement 'of the that shown' in Figure 1.

Although the invention has been heretofore described in connection with single-phase transformers, the aforesaid applies also tothe polyphase transformers. Figure 5 shows a transformer adapted for three-phase supply and Figure 6 illustrates the connections of the transformer, which is of the Scott type and in which the primary windings 4 4' are star-connected and the secondary windings 5 5' are connected in series with ea'ch other and with the 'auxiliary coll 'I across the welding electrode.

The transformer shown in Figure 5 is substantially like a single-phase transformentheonlydlfequipped with primary and secondary windings During no-load the limb 2 is traversed by the resultant magnetic flux of the two limbs I and 231 which. flux is therefore composed by two magnetic 'fluxes which are 90 displaced from each other. A portion of this resulting magnetic flux passes though air gap 8 and limb 3 generating in the auxiliary vcoil 'I a supplemental voltage which is in phase with the secondary voltage.-

In the arrangement illustrated in Figure 6 all three phases of the primary circuit supply current. These currents as well as the phase displacements are unequal. However, by means of condensers this lack of symmetry can be equalized to a large extent.

In order to avoid vibration of the movable limb 3, and eventually of yoke I of Figure 3. thesea parts may be hinged as shown in Figures 7 to Figure 7 represents a plan view of the end of the lower yoke I", Figure 8 is an elevation and Figure 9 a side view of the lower end of the limb 3. As shown in the drawing, the ends of the -twopmstobehmged together areslottedsoas-u to form dovetailed joints connected by a pivot pin 6.

The adjustment`of the limb I may be eiected for instance by means of the device shown in Figure 1, comprising a spindle I2 having a right and left hand thread, the threaded part being screwed into threaded bushings I3, I3", which are in turn fastened to 'yoke I and to limb I' respectively. Each position of the movable limb 3 corresponds to a certmn welding current or electrode diameter. These current intensities may be inscribed on a scale of a drum I4 which may be rotated by means of a band I5 connected to the said drum Il and to a winding drum I8 fitted to the spindle I2 respectively. 'I'he whole device is mounted inside oi a casing I`I provided with an opening I6. The spindle I2 projects through this casing I1 and is provided with a handwheel 25. By rotating this handwheel the air gap 8 is adjusted and the corresponding welding current intensities may be read on the drum I4 through the opening I6.

I claim:

1. In a transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeance arranged to form a substantially continuous'ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein a zone of reduced permeability, said second core being arranged relative to said first loop in magnetic shunt with said member and forming therewith a second magnetic loop, primary and secondary windings on said first core, and an auxiliary winding `encircling said zone and connected in series with said secondary windings to cause the voltage induced therein by that part -of the primary ux which is shunted through the second core to be added to the voltage induced in said secondary windings. y

2. In a transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeance arranged to form a substantially continuous ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein a zone of reduced permeability, said second core being arranged relative to said iirst loop in magnetic shunt with said member and forming therewith a second magnetic loop, primary and secondary windings on said ilrst core, and an auxiliary winding encircling said zone and connected in series with said secondary windings to cause the voltage induced therein by that part of the primary flux which is shunted through said second core to be added to the voltage induced in said secondary windings and further to cause the iiux induced in said second loop by the current in said auxiliary coil to pass through said member in the same direction as the magnetic iiux vinduced by the primary current in said first loop.

3. In a transformer, vin combination, a substantially U-shaped iron core, an iron member of relatively high permeance arrangedv to form a substantially continuous ferro-magnetic loop' with said core. a second substantially U-shaped ferro-magnetic core havinginterposed therein an adjustable Zone' of reduced permeability, said second core being arranged relative to said rst loop in magnetic shunt with said member to form therewith a second' magnetic 100D, means to vary the permeability of said zone, primary and secondary windings on said iirst core, and an auxiliary winding encircling said zone and connected in series with said secondary winding to cause the voltage induced therein by that part of the primary iiux which is shunted though the second core to be added to the voltage induced in said secondary winding.

4. In a transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeanoe arranged to form a substantially continuous ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein an adjustable zone of reduced permeability comprising, an'air gap which is bridged by an iron shunt of relatively high permeability at low flux densities in said second core and of relatively low permeability at high flux densities in said second core, said second core being arranged relative to said iirst loop in magnetic shunt with said member to form therewith a second magnetic loop, primary and secondary windings on said first core, and an auxiliary winding encircling said zone and connected in series with said secondary windings to cause the voltage induced therein by that part of the primary flux which is shunted through the second core tobe added to the voltage induced in said secondary windings.

5. In a transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeance arranged to form a substantially continuous ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein an adjustable zone of reduced permeability comprising an air gap which is bridged by a shunt having the magnetic chracteristics of Permalloy, said second core being arranged relative to said iirst loop in magnetic shunt with said member and forming a second magnetic loop therewith, primary and secondary windings on said rst core, and an auxiliary winding encircling saidv zone and connected in series with said secondary windings to cause the voltage induced therein by that part of the primary iux which is shunted through the second core to be added to the voltage induced. in said secondary windings.

6. In a transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeance arranged to form a ferro-magnetic loop with said core which is continuous but for a relatively short air gap interposed therein outside of said core, a second substantially U-shaped ferro-magnetic core having interposed therein a zone of reduced per meability, said second core being arranged relative to said iirst loop to shunt said member and to form therewith a second magnetic loop, primary and secondary windings on said first core, and an auxiliary winding encircling said zone and connected in series with said secondary windings vto cause the voltage induced therein by that part of the primary flux which is shunted through the second core to be added to the voltage induced in said secondary windings.

7. In Va transformer, in combination, a substantially U-shaped iron core, an iron member arranged to form a substantially continuous ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein a zone of reduced permeability, said second core being arranged relative to said iirst loop in magnetic shunt with said member and forming a second magnetic loop therewith, the cross sectional area of said member being substantially equal'to the sum of the cross sections of said cores, primary and secondary windings on said flrst core, and an auxiliary winding encircling said zone and connected in series With s aid secondary windings to cause the voltage induced therein by that part of the primary flux which is shunted through the second core to be added to the voltage induced in said secondary windings. A

8. In a. transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeance arranged to form a substantially continuous ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein a zone of reduced permeability comprising, an adjustable air gap arranged between relatively movable interengaging longitudinal projections and recesses integral with said frame and at opposite ends of said zone respectively, said second core being arranged relative to said first loop in magnetic shunt with said member and forming a second magnetic loop therewith, primary and secondary windings on said rst core, and an auxiliary winding encircling said zone and connected in series with said secondary windings to cause the voltage induced therein by that part of the primary iiux which is shunted through the second core to be added to the voltage induced in said secondary windings.

9. In a transformer, in combination, a substantially U-shaped iron core, an iron member of relatively high permeance arranged to form a substantially continuous ferro-magnetic loop with said core, a second substantially U-shaped ferro-magnetic core having interposed therein a zone of reduced permeability, comprising, an adjustable air gap shunted by relatively movable interengaging longitudinal projections and recesses integral with said frame and attached to said second core at opposite ends of said core respectively, to form a shunt for said air gap, said second core being arranged relative to said first loop in magnetic shunt'with said, member and forming a second-magnetic loop therewith,

primary and secondary windings on said first said auxiliary core being arranged relative to said` rst loops in magnetic shunt with said member and forming therewith lan auxiliary magnetic loop, primary and secondary windings on each of said plurality of cores, and an auxiliary winding encircling said zone and connected in series with said secondary windings to cause the voltage induced therein by the primary fluxes shunted through the auxiliary core to be added to the voltage resulting from said secondary windings.

EDUARD FRIES. 

